1. Field of the Invention
The present invention is directed to a dual mode cellular and cordless telephone and method for semi-automatic hand-over of calls between the two modes, and more particularly, to a dual mode telephone and method where dropped calls are re-established by the telephone without data from base stations or networks.
2. Discussion of the Prior Art
Wireless systems include PCS (Personal Communication System) or cellular and cordless systems. Examples of PCS/Cellular systems are AMPS (Advanced Mobile Phone Service), GSM (Global System for Communications), TDMA (Time Domain Multiple Access), CDMA (Code Division Multiple Access). Examples of cordless systems are DECT (Digital European Cordless Telephone System), FM (Frequency Modulation), spread spectrum, and the Bluetooth telephony profile. All systems comprise a handset and a base station. However PCS/cellular systems are nationwide, where the base stations serve many calls at the same time, and the distance between the handset and base station can be several miles. By contrast, cordless systems cover shorter distances and are typically for indoor use, such as in a home or office. Cordless base stations can support more than one handset, but the range is typically less than 1000 feet.
Both PCS/cellular and cordless systems are in widespread use and both are convenient. There are some handsets that support both cordless and PCS/cellular functions, but they are expensive. Bluetooth is a new technology that permits short-range wireless voice and data links between devices. One such application is cordless. Thus, a PCS/cellular handset could add cordless functionality at a low cost using Bluetooth. Accordingly, the number of dual mode cordless and PCS/cellular handsets could increase significantly.
There is a need to roam between cordless and PCS/cellular systems. In dual mode systems, communication is necessary between a cordless base station and a PCS/cellular network to facilitate hand-over of calls between the two different systems. However, conventional systems and methods for call hand-over are expensive and difficult to implement since, for example, strength of signals between handsets and base stations are monitored and communication paths of current calls are stored by the network or base stations for hand-over of calls or re-establishment of calls in case of a dropped call. Accordingly, there is a need to provide a cost effective system and method for call hand-over between two different systems.
The object of the present invention is to provide a dual mode handset that eliminates the problems of conventional dual mode handsets.
The present invention accomplishes the above and other objects by providing a wireless communication device for establishing communication with a remote terminal device through a cordless or a mobile base station. The wireless communication device has a cordless section and a mobile section. The cordless section is for communicating with a remote terminal device through the cordless base station in a cordless mode used for a cordless call. The mobile section is for communicating with the remote terminal device through the mobile base station in a mobile mode used for a mobile call.
A processor of the wireless communication device detects a drop of a current call using the cordless service, for example, and re-establishes the communication using the mobile service. The user may be prompted prior to call re-establishment. For outgoing calls, the last dialed number is stored and re-dialed for call re-establishment. For incoming calls, the caller ID is used for call re-establishment. When a cheaper service is detected during a call, the user is prompted and invited to use the cheaper service.